EMP Prepping: How To Build A Reliable Faraday Cage

An electromagnetic pulse that knocks out power across the country is one of the most terrifying disasters that could happen. Millions of people would slowly die of thirst, hunger, or disease, and millions more would die at the hands of starving looters.

There are many things you should do to prepare for an EMP, and one of the most important is building a Faraday cage. With it, you can keep certain items safe from the EMP. For example, two-way radios, shortwave radios, LED flashlights, solar battery chargers, and so forth. Radios, in particular, would be helpful, as you’d be able to figure out the nearest area that wasn’t affected by the EMP and head that direction.

A Faraday cage could be as simple as a microwave, an ammo can, or a metal trash can. But how well would a makeshift Faraday cage-like that actually work? It depends. If you are too close to ground zero and your cage isn’t very good, it might not work at all. The Faraday cage in this video, however, would probably work perfectly no matter where you are.

The video is by Canadian Prepper, and in it, he shows off what he calls his “EMP box”. He made it with a cheap aluminum crate, which you can see below.

It’s important that your Faraday cage has a good seal. If there is even a tiny slit between the lid and the container, the pulse could get through and fry your electronics.

To make sure that doesn’t happen, you’ll want to start by using sandpaper or a Dremel to remove any paint and smooth out any rough spots where the lid closes against the box. You can see what I mean in the image below.

Next, add some conductive copper tape around the edges that you sanded. You can probably get away with using aluminum tape, but better safe than sorry. See below.

Next, you need an inner liner that is non-conductive. Canadian Prepper got some custom molded laser cut foam. If that is something you’re willing to pay for, go for it. Otherwise, you could use something like cardboard or cloth.

Be sure to watch the video below for more information. Shortly after the 7-minute mark, he starts discussing the specific items he keeps in his Faraday cage.

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Comments

A better test is a portable AM radio, preferably tuned to the strongest local station station you can find.

Turn it on, loud, and put it in the box and seal it. If you can still hear station, the Faraday cage is leaking. (There is more energy in the EMP at the low end of the RF spectrum.)

For a better test, drag it out to the transmitter site (in your car, like), and repeat.

Shielding MAY be improved if the cage is connected to a GOOD low-impedance ground. You are trying to counteract something that has the characteristics of a direct lightning strike. Heavier (thicker metal) is usually better.

NAY! Best is” Double trash can, 20 gallon inside 30 gallon with both cans interior lined: sides, bottom, and lid lined with corregated works best. I have built 3 sets. Try the cell phone test to make sure all is sealed.
As Dave says above adhesive creates voids in seal.

But let’s face reality – so long as the gaps in your seal are smaller than the wave length of a micro-wave, your cage should work just fine.

For example, look at the screen in the door of a micro-wave oven. Those holes are so small that water tends to flow off rather then through. (I’ve taken a few blown ovens apart to use the screens as extremely fine sifters) – but the holes are so close together that you can see through them almost “as if” the screen didn’t exist – light waves get through, but not radio waves, not even MICRO-waves. (Otherwise, why have a light bulb inside the oven?)

However, a simple solution is a wrap around lid. It doesn’t have to be AIR tight, just light tight, like the door-less entrance to a dark room. You know, the kind where you make two right angle and one “U” turn. Of course, in restrooms, the walls are painted to reflect light – often there IS a light in the tunnel. Just you TRY to navigate one of those when the lights are out!

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